Heart failure (HF) is a debilitating, end-stage disease in which abnormal function of the heart leads to inadequate blood flow to fulfill the needs of the body's tissues. Typically, the heart loses propulsive power because the cardiac muscle loses capacity to stretch and contract. Often, the ventricles do not adequately fill with blood between heartbeats and the valves regulating blood flow may become develop leaks, allowing regurgitation or backflow of blood. The impairment of arterial circulation deprives vital organs of oxygen and nutrients. Fatigue, weakness, and inability to carry out daily tasks may result.
Current standard treatment for HF is typically centered around medical treatment using ACE inhibitors, ARBs, diuretics, and beta blockers. It has also been demonstrated that aerobic exercise may improve exercise tolerance, improve quality of life, and decrease symptoms. Cardiac surgery has also been performed on a small percentage of patients with particular etiologies. Although advances in pharmacological therapy have significantly improved the survival rate and quality of life of patients, some HF patients are refractory to drug therapy, have a poor prognosis and limited exercise tolerance. In recent years cardiac pacing, in particular cardiac resynchronization therapy (CRT), has emerged as an effective treatment for many patients with drug-refractory HF.
Long-term clinical benefits of CRT are influenced by patient selection, lead placement, and device programming. For example, a variety of intracardiac electrogram (IEGM) based algorithms have been developed to predict which atrioventricular (AV) and interventricular conduction (VV) delays will facilitate maximizing clinical benefits. For a viable myocardium, mechanical contraction is coupled with electrical conduction.
In multipoint pacing (MPP), two left ventricular (LV) pulses are delivered during a single pacing cycle. MPP has been shown to increase LV reverse remodeling, increase LV function acutely, convert non-responders to CRT into responders, and further improve response in those who respond to conventional CRT. Further, use of MPP has been shown to result in increased LV function three to twelve months after therapy, as compared to conventional CRT. Although MPP is beneficial, MPP also generally reduces device longevity, as it requires more power than conventional CRT methods. Accordingly, it would be desirable to realize the benefits of MPP at a reduced power consumption.